Well, you're gonna have to slow down with the "XMB"/Dev talk, I'm computer literate, but the PS3 is relatively new to me. Course, when I got home and realized that it didn't update normally AND it didn't have a hard drive, I was majorly pissed and believed that I'd be scammed. Although, judging from the quality of the truck and the demeanor of the heavily tattooed, mustachiod man in the wifebeater, I'm gonna be an ass and assume that he thought he was selling me a broken piece of crap (having already sold the hard drive to some third party I'll assume).
As for your second question, I can't play BD movies and I can't play dvds either (though I don't know if normal PS3s play dvds I suppose since I've never been able to play around with a normal PS3.) I believe it was originally a 60 gig, though that's from the very questionable word of a man in a wifebeater (apologies to those who favor the wifebeater). I suppose that claim is backed up by the number of usb ports and the fact I haven't had any trouble playing PS2 games.
I also notice a Debug Systems menu (it's got a little star by it) in the main menu screen. There's a load of little options there that I've very little idea what to do with.